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M.A. Fidanza, P.F. Colbaugh, M.C. Engelke, S.D. Davis, and K.E. Kenworthy

Fairy ring is a common and troublesome disease of turfgrasses maintained on golf course putting greens. Type-I fairy ring is especially destructive due to the development of hydrophobic conditions in the thatch and root zone, thus contributing to turfgrass injury and loss. The objective of this 2-year field study was to evaluate the application and novel delivery method of two fungicides and a soil surfactant for curative control of type-I fairy ring in a 20-year-old creeping bentgrass [Agrostis palustris (synonym A. stolonifera)] putting green. In both years, all treatments were applied twice on a 28-day interval. In 1998, flutolanil and azoxystrobin fungicides were applied alone and in combination with Primer soil surfactant by a conventional topical spray method, and fungicides without Primer applied via high-pressure injection (HPI). Acceptable type-I fairy ring control was observed in plots treated with flutolanil plus Primer, HPI flutolanil, azoxystrobin alone, azoxystrobin plus Primer, or HPI azoxystrobin. In 1999, treatments were HPI flutolanil, HPI flutolanil plus Primer, HPI azoxystrobin, HPI water only, and aeration only. Acceptable type-I fairy ring control was observed in plots treated with HPI flutolanil plus Primer or HPI azoxystrobin. HPI of fungicides alone or in combination with a soil surfactant may be a viable option for alleviating type-I fairy ring symptoms on golf course putting greens.

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Vladimir Orbovic, John L. Jifon, and James P. Syvertsen

Urea solutions, with or without non-ionic (X-77) and organosilicone (L-77) surfactant, were applied to Citrus leaves and isolated cuticles to examine adjuvant effects on urea uptake and leaf net gas exchange. When compared to X-77, L-77 exhibited superior features as a surfactant, resulting in smaller contact angles of droplets deposited on teflon slide. Both L-77 and X-77 had a strong effect on penetration rate of urea within first 20 min of experiment. Effect of L-77 on urea penetration rate decreased quickly within next 20 min, whereas the effect of X-77 was sustained over a 24-h period following application. When compared to solution of urea alone, addition of X-77 to urea resulted in significant increase of the total amount of urea that penetrated the cuticles. The effect of L-77 was smaller, although the total amount of urea that penetrated the cuticles within a 4-day period was similar for both surfactants. Solutions of either urea alone, urea+L-77 and urea+X-77, or L-77 alone, induced a negative effect on net CO2 assimilation (ACO2) for 4 to 24 h after they were sprayed onto leaves. X-77, when applied alone, had no effect on ACO2. Scanning electron microscopy revealed that 1 h after application, leaf surfaces treated with X-77 appeared to be heavily coated, as opposed to those treated with L-77, which appeared similar to untreated control leaves.

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Royal G. Fader, Patricia Luque, and Martin J. Bukovac

Foliar application of plant growth regulators (PGR) is an established horticultural practice. We are using a finite dose system to examine diffusion of 14C-labeled PGRs, primarily napththaleneacetic acid (NAA), from aqueous droplets and deposits through enzymatically isolated plant cuticles (CM) as affected by spray adjuvant chemistry, solution pH, and epicuticular wax. Recent studies have focused on a nonbuffered aqueous medium, which approximates field application conditions. Despite the negligible buffering capacity of the spray solution, there were significant differences in NAA diffusion with solution pH. At pH 3.2, NAA (pKa = 4.2) diffusion was two-fold greater than at pH 5.2. Additives (surfactants, urea, and urea:NH4NO3, 1:1 mixture) in the spray solutions increased the initial rate and absolute amount of NAA diffused. The polyethoxalated octylphenol surfactant (Triton-X) TX-45 (EO 5.5) enhanced rate and quantity of NAA diffusion. This enhancement was observed with CM, but not after removal of the epicuticular waxes, implicating an interaction between surfactant and waxes. Urea, over a four-fold concentration range, increased NAA diffusion 5% to 31% after 144 h. The urea:NH4NO3 mixture increased NAA diffusion to a greater extent at pH 5.2 (+136%) than at pH 3.2 (+8.4%) after 144 h.

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Young-Ki Park, Byung-Hoon Min, Heawon P. Choi, and Jung-Myung Lee

A series of experiments were conducted to investigate the effects of chlorocholine and similar compounds such as choline, chlorocholine chloride (CCC or chlormequat) and other compounds on the rooting and seedling quality for transplanting. The growth of shoot and root and the ratio of shoot/root were influenced and consequently the seedling quality was improved by chlorocholine treatment. Mungbean bioassays for plant hormone revealed that rooting was promoted and shoot growth or stem elongation was inhibited by the treatment. Addition of other PGRs such as atonik, vitamins and surfactants to chlorocholine solution significantly promoted the rooting of mungbean cuttings as well as the rooting of cutting of sweet potato, cucumber, and watermelon.

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Michael W. Smith, Becky S. Cheary, and B. Scott Landgraf

A low leaf Mn concentration was detected in bearing pecan (Carya illinoinensis Wangenh. C. Koch) trees growing in an alluvial soil with an alkaline pH. Trees lacked vigor and leaves were pale in color, but there was no discernible leaf chlorosis or necrosis. Three foliar applications of MnSO4 beginning at budbreak, then twice more at 3-week intervals at rates of 0 to 3.3 kg·ha-1 of Mn increased leaf Mn concentration curvilinearly, and alleviated leaf symptoms. Results indicated that three foliar applications of MnSO4 at 2.15 kg·ha-1 of Mn plus a surfactant were adequate to correct the deficiency.

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Hector R. Valenzuela, Osamu Kawabata, and Harry Yamamoto

Methanol sprays reportedly increased yields of several crops in Arizona by 50 to 100 percent (Nonomura and Benson PNAS 89:9794(1992). Reports from other parts of the country have shown conflicting results with regards to the effect of methanol sprays on yields of horticultural crops. Several greenhouse and growth chamber (controlled temperature. day length, and photosynthetic photon flux) experiments were conducted to evaluate the effect of methanol sprays on the growth and productivity of several vegetable crops in Hawaii. Treatment spray solutions consisted of 20-25% methanol, 0.5% low biuret urea. 0.001% chelated iron, and 0.02% surfactant. Control sprays only contained urea, chelated iron, and surfactant. Each experiment consisted of at least 5 weekly methanol sprays. Flowering cabbage, Brassica campestris var. parachinensis, had greater biomass production when sprayed with methanol in the late summer months. Similar results were obtained with choi sum in a 2 by 2 factorial experiment with methanol and water stress treatments. However, choi sum did not respond to methanol treatments in follow-up greenhouse trials. perhaps attributable to the shorter and Overcast days experienced in the fall and winter. Okra, chili pepper, and eggplant showed no response to methanol sprays. Okra showed a trend toward increase yields in response to methanol sprays, but differences were not significant. Follow-up studies in the greenhouse and in the field, which include evaluation of photosynthetic efficiency through chlorophyll fluorescence determinations will be presented.

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J.P. Syvertsen and M. Salyani

The effects of three highly refined petroleum spray oils and of ambient vapor pressure on net CO2 assimilation (A) and stomatal conductance of water vapor (gs) of single grapefruit (Citrus paradisi Macf.) leaves were investigated. Overall, gs of various-aged leaves was decreased by a large leaf-to-air vapor pressure difference (VPD). In the first experiment, oils with midpoint distillation temperatures (50% DT) of 224, 235, and 247C were applied with a hand atomizer at concentrations of 0, 1%, and 4% oil emulsions in water and 100% oil, all with 0.82% surfactant (by volume). There was a tendency for oils of the two higher DT to decrease net gas exchange during a subsequent 12 days, but significant differences could not be attributed to oil DT. Both A and gs were reduced by the two higher concentrations of oil mixtures. In the second experiment, a commercial airblast sprayer was used to apply the 224C oil at 4% or the 235C oil at 2% and 4% mixtures plus surfactant under field conditions. There were no significant effects of oil treatments on net gas exchange of leaves either measured under moderate VPD outdoors 1 day after spraying or under low VPD in the laboratory 2 days after spraying. No visible phytotoxic symptoms were observed in either experiment.

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Stephen C. Myers, Steven McArtney, Stuart Tustin, Wendy Cashmore, and Richard Mangin

Foliar applications of monocarbamide dihydrogensulfate (D-88, Unocal Chemicals Division) at rates of 0, 2.5 ml/1, 3.75 ml/1 or 5.0 ml/1 were made to mature apple trees of “Fuji”, “Royal Gala” or “Braeburn” on MM106 root-stock. Treatments were applied dilute when spurs were at 95% full bloom. D-88 was applied at 5.0 ml/1 to “Fuji” at three different times during the day (0730, 1400 or 1810) with and without surfactant in an attempt to evaluate the effect of different atmospheric and drying conditions. Fruit set (number of fruit per 100 flower clusters) was determined after natural fruit drop.

D-88 had no effect on fruit set of “Royal Gala” or “Braeburn”. There was a linear effect between D-88 rate and fruit set on “Fuji”, with the 5.0 ml/1 rate reducing set by 30%. D-88 affected the number of fruit at individual fruiting sites, most significantly the percentage of flower clusters setting 3 fruits decreasing with increasing rate. Timing and surfactant had no effect.

Fruit finish, mean fruit weight, seed number and soluble solids concentration were measured at harvest.

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Benjamin Mullinix, Gerard Krewer, Scott Nesmith, S. Scarborough, J. Clark, and D. Stanaland

Five experiments were run using surfactants and gibberellic acid (ProGibb). Fruit set is a problem with rabbiteye blueberry plants. Gibberellic acid sprayed on plants when they are in bloom does enhance fruit set. Currently, it costs $247/ha to achieve this enhanced fruit set. `Tifblue', `Climax', and `Woodard' cultivars were used in on-farm experiments. Usually, applications of 80 + 80 are used. With use of X-77 and L-77 surfactants, rates were reduced to 40 + 40. Other rates examined were 32 + 32, 24 + 24, 16 + 16 + 16. Fruit was enhanced significantly over no spraying. Airblast I sprayer performed better PropTec, whether used for day or night applications. Spraying slanting downward produced greater fruit set than from the side. E1: Trt = 15 – 20, C = 11 lb/lo. E2: 32 + 32 = 12, 16 + 16 = 7 lb/lo. E3: AB = 64, PT = 48 %FS; Trt = 56, C = 35 %FS; `C' = 73, `T' = 39 %FS. E4: 5% FS with Trt; `T' = 53, `W' = 57 %FS. E5: 30 + 30 = 87, – 40 + 40 = 80 %FS.

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Ross E. Byers

AVG applied 2 to 6 weeks before the optimum harvest date for several cultivars dramatically reduced pre-harvest fruit drop. The loss of fruit firmness and starch loss after the optimum harvest date was reduced by AVG sprays. The development of watercore in `Starkrimson Delicious' and `York' and maturity cracking in `Rome' and `Golden Delicious' were delayed and/or prevented by AVG. Color development was slightly delayed for most red cultivars and `Golden Delicious'. Soluble solids concentration was generally unchanged. Airblast applications of 123 g·ha–1 AVG was no more effective than a standard rate of NAA (28 to 56 g·ha–1), but rates of 248 g·ha–1 AVG and above were more effective than NAA for most cultivars. When fruit were left on the tree for periods of 3 to 5 weeks after the optimum harvest date, NAA hastened the loss of fruit firmness and starch and NAA increased watercore of `Delicious' and maturity cracking of `Golden Delicious' and `Law Rome'. Soluble solids and red color were generally unaffected by NAA. Ethephon sprays hastened the rate of fruit drop. When NAA was tank mixed with ethephon, NAA delayed fruit drop caused by ethephon, but AVG did not. The use of superior oil or Regulaid surfactant did not affect NAA or AVG responses; however, the silicone surfactant Silwet L-77, in one experiment, promoted the effectiveness of AVG. Tank mixing NAA or AVG with pesticides (Guthion + Lannate + Captan) did not affect the responses of AVG or NAA on fruit drop.